Stabilized polyolefins



United States Patent ice ,jjfiff'fi are known but these in general exhibit a lesser stabilizing 3,422,059 elfect, particularly on repeated laundering, than the esters STABILIZED POLYOLEFINS of the present invention. It is preferred that at least one George Wright Taylor and Derek Harold Wood, Harrogate, England, assignors to imperial Chemical Industries Limited, London, England, a corporation of Great substituent alkyl or alkoxy group (any one or more of the R R R and R groups) should be present in Britain the phenolic nuclei ortho to the phenolichydroxyl group, No Drawing. Filed Mar. 28, 1966, Ser. No. 537,690 for in this y P a y if this substituent group is 5 Claims priority, application Great Britain, May 3, 1965, bulky one, the antioxidant effectiveness of the phenolic 18,516/ 65 portion of the diester is enhanced due to steric hinderance U.S. Cl. 260-4585 9 Claims 10 of the phenolic hydroxyl' group. Compounds according to CL C08f 45/58" Cosf 29/02; (307C 69/76 the invention wherein the phenolic groups each have two bulky substituents, as for example tertiary butyl groups, each in an ortho position with respect to the phenelic hydroxyl group, are very effective stabilizing substances. 5 Diesters according to the invention protect polyolefins into which they are incorporated against oxidative degradation and in general 0.05 to 5% by weight of the polyolefin is an etfective amount. As polyolefins are also subject to other degradative effects it is often desirable to incorporate one or more additional stabilizing substances, as for example an ultraviolet light absorber or thermal stabilizer.

Diesters according to the invention are incorporated into polyolefins by any method, as for example mixing of 5 the powdered polyolefin with the solution of the additive in a volatile solvent followed by drying and granulation of the mixture or by mixing the additive directly into the softened polyolefin in a hot roll or Banbury mixer.

The present invention may be applied to any polyolefin 30 and we have found it to be most useful for improving the stability of stereoregular polyolefins, particularly those, as for example stereoregular poly(4-methylpentene-l) or isotactic polypropylene, from which useful textile fibres or filaments may be produced. The examples which follow illustrate the invention and the manner in which it may be performed. In these examples all parts are by weight.

This invention relates to stabilized polyolefins, in particular to polyolefin compositions which, in the form of shaped articles, retain their stability after many laundry treatments.

It is well known that polyolefins, in particular those containing tertiary carbon atoms, are subject to degradation by several influences, as for example ultra-violet light, heat and oxygen. Many attempts have been made to stabilize the polyolefin material against these degradative influences with varying degrees of success. Unfortunately some of the most effective stabilizing agents are unsatisfactory as stabilizers for polyolefins in the form of shaped articles, as for example, filaments and fibres 'which are subject to solvent and washing treatments as in dry cleaning and laundering, for the stabilizing effect is rapidly lost by extraction of the stabilizer or stabilizers from the articles.

We have now found that certain diol dialkanoates are very effective antioxidants in polyolefin articles and that such articles are highly resistant to, for example, laundermg.

According to the invention we provide a stabilized polyolefin composition wherein there is incorporated either alone or in combination with other polyolefin stabilizers an antioxidant which is a diol dialkanoate of the formula where R R R and R are hydrogen, alkyl, or alkoxyl EXAMPLE 1 groups, n is 2 or 3, x and y have the value 0, 1, 2, or 3 and A is derived from a diol said diol being an alkane diol, a thiodialkanol or a poly(ethylene glycol). Thus, A

Preparation of decamethylene diol di[bis(3,5-di-tert.- butyl-4-hydroxyphenyl) acetate] may be straight-chain alkylene or monothioalkyleue con- Me hyl i-(3,5-dituty -4-hydroxyphenol) acetate taining 3-10 carbon atoms. (7.2 parts) and decamethylene diol (1.3 parts) are heated 'Diol dialkanoates according to the invention may be get er nder a flow of nitrogen gas. When the mixconveniently prepared by t r interchange b t th ture becomes molten tetra-n-butyl titanate solution in relatively high boiling diol and a lower alkyl ester, as n-butanol (1 P in 4 Parts Of 1311131101) is added s catafor example, the methyl ester of the appropriate phenolic lyst for the ester interchange reaction. The mixture is then acid. The ester interchange reaction may be facilitated by h ated to 160170 C. for Seven hours, Cooled and the the use of an appropriate catalyst, as for example, zinc Solid P decamethylene diol y or calcium acetate or a tetraalkyl titanate. This method y yp vU after recrystallization fr m may be used to prepare diol dialkanoates having different Petroleum ether (boiling range has a meltphenolic groups at the two ends of the dialkanoate molecg Point of The Yield of Product is 77% ules by carrying out the ester interchange between the 60 0f the theoretical am Imtdiol and a mixture of lower alkyl esters of different Effectiveness of stabilization phenolic acids. In this case a mixture of products would be formed including diesters having different phenolic The Hester Part) Prepared as above is incorporated groups at the ends of the molecule. Such mixtures may IP PY (100 P i @gether with a thermal be used to stabilize polyolefins without separation of the F": i w -I B l P P and individual diesters therein the mixture is melt spun and drawn into filamentary yarn Preferred diols from which esters according to the inof 720 denier having 144 filaments and 4 films p inch vention are derived are those which contain at least 3 of twist inserted therein. Hanks of the yarn together with carbon atoms '01 at least two ethylenoxy groups similar yarn containing 3. COIIlIIlel'Cifll antioxidant (the Phenolic diesters wherein a single phenolic group is condensation product from 3-methyl-6-tert-butylphenol present in the carboxylic acid from which they are derived and crotonaldehyde) in place of the foregoing antioxidant are subjected to repeated cycles of a laundering process, which consists in agitating the hanks in boiling soap solution (5 parts of textile soap and 2 parts of sodium carbonate in 1000 parts of water) for 1 hour following by rinsing in fresh water and drying at 140 C. for one hour in a Wallace ageing oven until the hank at least partially breaks when subjected to a vigorous tug with the fingers.

Yarn stabilized with antioxidant prepared as described above survives 23 laundering cycles Whereas that containing the commercial antioxidant survives only 89 cycles.

In an even more severe laundering process, wherein the hanks are boiled in the soap solution for 30 minutes and dried in a Wallace oven at 150 C. for 1 hour, yarn stabilized with the foregoing antioxidant according to the invention survives 17 laundering cycles and the control yarn containing the commercial antioxidant survives 6 cycles.

EXAMPLE 2 Preparation of hexamethylene diol di-[bis-(3,5 di-tertbutyl-4-hydroxyphenol)-acetate] Methyl di-(3,5-di-tert-butyl-4-hydroxyphenyl) acetate (14.5 parts) and hexamethylene diol (1.8 parts) are heated tigether under a flow of nitrogen gas at 160-170 C. for about 16 hrs. and a trace of tetra-n-butyl titanate is then added as a catalyst and the mixture heated at 170- 180 C. for a further 23 hours. The mixture is cooled and the solid product hexamethylene diol di-[bis-(3,5-ditert-butyl-4-hydroxy-phenyl) acetate] after recrystallization from petroleum ether (boiling range 100l20) has a melting point of 173181 C. The yield of product is 80% of the theoretical amount.

When this diester ((0.5 part) is incorporated into isotactic polypropylene (100 parts) together with dilaurylfi,fi-thiodipropionate (0.5 part) and spun into yarn as described in Example 1, the resultant yarn survives cycles of laundering according to the more severe laundering process (drying at 150 C.) of Example 1.

R1 I l I I noocm).cooxoo o (errata EXAMPLE 3 Preparation of decamethylene diol di-[4,4-bis-(2-methyl- 4-hydroxy-S-tert-butylphenyl) butanoate] Ethyl 4,4-bis 2-methyl-4-hyd roxy-S-tert-butylphenyl) butanoate (8.8 parts) and decamethylene diol (1.7 parts) are heated together under a fiow of nitrogen gas at 170 C. for about 16 hours and a trace of tetra-n-butyl titanate is added as a catalyst and the mixture heated at 170 C. for a further 8 hours. The mixture is cooled and the solid product decamethylene diol di-[4,4-bis-(2-methyl-4-hydroxy-5-tert-butylphenyl) butanoate] after recrystallization from petroleum ether has a melting point of l20-l24 C. The yield of product is 76% of the theoretical amount.

When this diester (0.5 part) is incorporated into isotactic polypropylene (100 parts) together with dilaurylfi,fi'-thiodipropionate (0.5 part) and spun into yarn as described in Example 1, the resultant yarn survives 12 cycles (drying temp. 150 C.) of the severe laundering process.

EXAMPLE 4 Preparation of 4,4'-thiodibutanol di-[bis-(3,5-di-tertbutyl-4-hydroxyphenyl) acetate] Methyl di-(3,5-di-tert-butyl-4-hydroxyphenol) acetate (7.2 parts) and 4,4'-thiodibutanol (1.3 parts) are heated together under a flow of nitrogen gas. When the mixture becomes molten a trace of tetra-n-b yl tilflnate 801M011 in n-butanol (1 part in 4 parts of bntanol) is added as catalyst for the ester interchange reaction. The mixture is then heated to l-200 C. for 2 /2 hours, cooled and the solid product 4,4-thiodibutanol di[bis(3,5 di-tertbut-yl-4-hydroxyphenyl) acetate] is washed with petroleum ether (boiling range 4060 C.) to yield a product melting at 6976 C. The yield of product is 55% of the theoretical amount.

When this diester (0.5 part) is incorporated into isotactic polypropylene parts) together with dilauryl- B,;8-thiodipropionate (0.5 part) and spun into yarn as described in Example 1, the resultant yarn survives 12 cycles (drying temp. C.) of the severe laundering process.

As one skilled in the art may judge from the foregoing examples diesters according to the invention are effective antioxidants for polyolefins and incorporated therein are very resistant to severe laundering and drying treatments. Simpler esters wherein only a single phenolic group is present at the ends of the diester molecule, as for example the following compounds:

I X k and wherein X is a tert-butyl group, survive only 3-6 cycles of the severe (drying at 150 C.) laundering process.

What we claim is: 1. A stabilized poly-a-olefin composition comprising the poly-a-olefin and, as a stabilizer therefor, an antioxidant diol dialkanoate of the formula:

R3 I I -0H L R ll wherein R R R and R are selected from the group consisting of hydrogen and lower alkyl, 21 is 2 or 3, x and y have the value 0, l, 2 or 3 and A is derived from a diol selected from the group consisting of an alkane diol and monothiodialkanol.

2. A stabilized poly-a-olefin composition according to claim 1 wherein the phenolic hydroxyl groups of the diester are sterically hindered.

3. A stabilized poly-a-olefin composition according to claim 2 wherein the phenolic hydroxyl groups of the diester are sterically hindered by tertiary-butyl groups.

4. A stabilized poly-u-oiefin composition according to claim 1 wherein 0.05-5% by weight of the polyolefin of the diol dialkanoate is present.

5. A stabilized poly-tz-olefin composition according to claim 1 wherein the poly-u-olefin is a stereoregular polya-olefin.

6. A stabilized poly-a-olefin composition according to claim 5 wherein the poly-a-olefin is stereoregular poly(4- methylpentene-l) or isotactic polypropylene.

7. A stabilized poly-u-olefin composition according to claim 1 wherein the antioxidant is selected from the group consisting of decamethylene diol di[bis(3,5-di-tert.-butyl- 4-hydroxyphenyl) acetate]; hexamethylene diol di-[bis- 3,5 di-tert.-butyl-4-hydroxyphenyl)-acetate]; decamethylene diol di-[4,4-bis-(2-methyl-4-hydroXy-5-tert.-butylphenyl) butanoate; and 4,4'-thiodibutan01 di-[bis-(3,5-ditert-butyl-4-hydroxypheny1) acetate].

8. A stabilized poly-a-olefin composition according to claim 1 wherein R R R and R are each lower alkyl, at 5 least one of R and R and at least one of R and R being tertiary-butyl; n is 2 or 3; x and y have the value 0, 1, 2 0r 3 and A is straight-chain alkylene 0r monothioalkylene containing 3-10 carbon atoms.

6 References Cited V. P. HOKE, Assistant Examiner.

US. Cl. X.R.

9. Yarn comprising a stabilized poly-a-olefin composi- 10 260 45 95, 469, 470

tion according to claim 1. 

1. A STABILIZED POLY-A-OLEFIN COMPOSITION COMPRISING THE POLY-A-OLEFIN AND, AS A STABILIIZER THEREFOR, AN ANTIOXIDANT DIOL DIALKANOATE OF THE FORMULA: 